Aging is the major risk factor for Alzheimer?s disease (AD). Numerous studies have confirmed that physical exercise has positive effects in patients with AD and other neurodegenerative disorders. The majority of the studies examining the effect of physical exercise in animal models of neurodegeneration have reported neuroprotection, improved memory and cognitive performance. The molecular mechanisms of the interactions between the non-neuronal systems involved in the physical/aerobic exercise and brain, however, remain poorly understood. The antiaging protein, a-Klotho, has well-known neuroprotective activity, and recent studies demonstrated that systemic elevation of a-Klotho protein in transgenic mice or injection of soluble ?-Klotho fragment, enhanced cognition and neural resilience in young, aging, and a murine disease model. Recent reports have suggested that a-Klotho levels decline in brain of animal models of AD. It has been recently shown that physical aerobic exercise increases the circulating levels of a-Klotho, and we have found that direct muscle contraction via neuromuscular electrical stimulation significantly enhanced a-Klotho expression in the hippocampus. These findings raised the novel hypothesis that skeletal muscle may be a regulator of circulating a-Klotho. We posit that muscle-induced stimulation of a-Klotho may play a role in the beneficial effect of exercise on cognitive outcomes. Importantly, it has been established that signals from periphery to the CNS are transmitted through mechanisms highly specific to choroid plexus (CP) epithelium, and physical exercise increases the release and amount of extracellular vesicles into the circulation. Our preliminary data demonstrate that a-Klotho is detectable at high levels in exosomes isolated from plasma, and that muscle contractile activity increases the release and amount of a-Klotho-containing exosomes in circulation. We also show that the exosomal cargo can transmit a signal to cells in vitro, thus affecting the expression level of intracellular proteins. We hypothesize that the effects of physical exercise on CNS are results of signals generated in peripheral muscles and transmitted to the brain via the CP epithelium. The signals are associated with and depend on increased circulating levels of anti-aging protein, a-Klotho, released by muscles within exosomes. This interdisciplinary research will integrate the expertise of AD researchers experienced with AD animal models, analysis of AD-like pathology and omix approaches (R. Koldamova & I. Lefterov), established researchers in biology of a-Klotho, rehabilitation, and aging (F. Ambrosio) and cell biology (C. St Croix). The goal of this proposal is to further our understanding of the interactions between a-Klotho expression in skeletal muscles, physical activity and brain, and to elucidate the relationship of age-related changes in skeletal muscle and progression of AD. Aim 1: To determine if the effects of physical exercise on phenotype and gene expression in the hippocampus and cortex are mediated by a-Klotho. Aim 2: To reveal the effect of muscle training on exosomal cargo in plasma and CSF, and to integrate their proteomic and miRNA profiles with the phenotype and brain transcriptomes. Aim 3: To elucidate the role of Choroid Plexus and a-Klotho in communicating signals from peripheral muscles to CNS.